Treatment of transparent material



Patented Jan. 17, 1928.

- UNITED STATES,

PATENT OFFICE.

CHARLES E. SWETT, OF WEST ROXBURY, MASSACHUSETTS, ASSIGNOR TO UNITED STATES ENVELOPE COMPANY, OF SPRINGFIELD, MASSACHUSETTS, A- CORPORA- TION OF MAINE.

TREATMENT OF TRANSPARENT MATERIAL.

No Drawing.

The present invention relates to the treat I ment of transparent material, for the purpose of reducing the glare, or reflection of light, from its surface. The invention is particularly applicable to the treatment of such material as is used for the transparent patches or panels of so-called window envelopes, i. e., the type of envelope having an opening therein, over which is cemented a covering of glassine paper or other transparent or semi-transparent material, such as a film of gelatin, or of celluloid or other suitable cellulose derivative. Such transparent material as glassiue paper and the like is characterized by its homogeneous texture and by the fact that it presents a smooth and more or less glazed surface.

In window envelopes as thus manufactured a troublesome feature is the glare or reflection of light from the surface of the transparent patch material, this giving rise to objection on the part of those required to handle numbers of such envelopes, as for instance, in the sorting of mail, particularly when the light falls at a small angle from the plane of the surface. The reduction or elimination of this glare, without substantial sacrifice of the transparency of the panel material is the primary object of the prescut invention.the same involving the application to the surface of the material of a suitable treating solution which is adapted, upon evaporation, to leave said surface in a matt or non-glare condition.

While such treatment, as contemplated by my invention, may be applied after the transparent patches or panels are incorporated in the envelopes, it is preferable, for manufacturing purposes, totreat the panel material in bulk, and for this reason, in the production of the matt surface it is of im portance to maintain, unimpaired, those characteristics of the patch material which allow it to be successfully manipulated, m'echanically, in a window envelope machine, and in particular (1) to avoid any undue warping or cockling of the transparent material, due to the use of too much water in the treating solution; (2) to preserve, in said matt surface, the same ability of the patch material to be attached securely to the envelope by the water-soluble cement or mucila e ordinarily em loyed in window enve ope machines; and (3) to insure that the Application filed March 14, 1923. Serial No. 625,166.

treated surface shall notfiake off, or heconie l bruised or disfigured by the mechanical handling which the patch undergoes 111 a win- .dow envelope machine.

any invention or discovery; in both methods a non-aqueous solvent, such as alcohol, benzol, or the like, is employed to hold the glaredeadening material in solution, thus avoiding the warping or cockling which an excess of water invariably produces in trans= parent'panel or patch material. According to one method, alcoholic solutions respectively of tartaric acid and-potassium acetate are brushed onto the panel material, one after the other, it being immaterial which is first. The evaporation of the alcohol leaves the patch material sub- .stantially as transparent as before, but with a firmly adherent fine deposit of acid potassium tartrate, or cream of tartar, the effect of which is to render the surface matt. Such matt surface is characterized by the fact that it offers no handicap to the attachment of the patch or panel to the body of the envelope by a water-soluble cement or mucilage, and furthermore, the union of the glare-deadening material with the panel material is so complete that the treated surface is entirely free from any disfigurement or bruising, 'or from any tendency to flake off, during the mechanical handling which the patch or panel undergoes in a window envelope machine.

The other method of treatment contemplated by my invention involvesthe use of an alcoholic solution of soap, as for in stance, the soda soap of the more fluid fatty acids of cocoanut oil, in the proportion for instance of 80 parts alcohol and 20 parts of soap. This solution is brushed onto the surface of the patch material and after evaporation, the patch material is substantially as transparent as before, but with a finely reticulated or pebbly surface which greatly reduces the surface reflection of light, or glare. Said matt surface offers no obstruction to the attachment of the patch to the envelope by an aqueous cement or mucilage,

and is not subject to disfigurement or bruising under ordinary conditions of mechanical handling in a window envelope machine.

Under both of the above described methods, the desired result isobtained by 5 the application of a solution or solutions adapted, on evaporation, to leave the treated surface in a matt and substantially glareless condition. My invention resides in the production of a matt surface by such a treatlu ment, Without substantial sacrifice of transparency, and without impairing the capacity of the material to be handled in a window envelope machine; it is obvious that glaredeadening substances other than cream of 15 tartar or soap may be employed in a manner the same or similar to that described above, and I do not limit myself to the use of these specified substances except as set/ forth in certain of the appended claims.

I claim, v 20 1. The herein described treatment of transparent material by depositing cream of tartar on the surface by double decomposie tion.

2. The herein transparentmaterial, which; consists in applying thereto alcoholic solutions, -respec tively, of tartaric acid and potassium acetate, and thereafter evaporating the alcohol.

CHARLES E. SWETT.

described treatment of 25 i 

